Android sqlite查询什么都不返回

Question

App is supposed to take an ingredient and search a database and return stuff like calories and so on. I just opened the file from Assets and copied it, opened the copy and make a table (supposedly; I ran try catch(exception)s on them and it said they were successful). But I try to run a query it gives an error "cannot covert nutr_grabber.mainactivity.usdProto to int". If I try using query.Energ_Kcal it gives no error but returns nothing at all. Any ideas?

using System;
using Android.Views;
using Android.Content;
using Android.Runtime;
using Android.App;
using Android.Widget;
using Android.OS;
using Android.Content.Res;
using System.IO;
using SQLite;
using System.Linq;
using Android.Database.Sqlite;

namespace nutr_grabber
{

    [Activity(Label = "nutr_grabber", MainLauncher = true, Icon = "@drawable/icon")]
    public class MainActivity : Activity
    {
        string str1;

        // Android needs a databse to be copied from assets to a useable location
        public void copyDataBase()
        {
            var dbPath = System.IO.Path.Combine(System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal), "UsdDataProto.db");

            if (!System.IO.File.Exists(dbPath))
            {
                var dbAssetStream = Assets.Open("UsdDataProto.db");
                var dbFileStream = new FileStream(dbPath, FileMode.OpenOrCreate);
                var buffer = new byte[1024];

                int b = buffer.Length;
                int length;

                while ((length = dbAssetStream.Read(buffer, 0, b)) > 0)
                {
                    dbFileStream.Write(buffer, 0, length);
                }

                dbFileStream.Flush();
                dbFileStream.Close();
                dbAssetStream.Close();
            }
        }

        protected override void OnCreate(Bundle bundle)
        {
            base.OnCreate(bundle);

            // makes the database
            try
            {
                copyDataBase();
                new AlertDialog.Builder(this)
                    .SetMessage("Database created ...")
                    .Show();
            }
            catch(Exception e)
            {

                new AlertDialog.Builder(this)
                    .SetMessage("Database not created ...")
                    .Show();                  

            }


            // Set our view from the "main" layout resource

            SetContentView(Resource.Layout.Main);


            //set widgets
            TextView message = FindViewById<TextView>(Resource.Id.message);
            EditText ingred = FindViewById<EditText>(Resource.Id.enterHere);
            Button search = FindViewById<Button>(Resource.Id.search);

            //open sqlite connection, create table
            var Path = System.IO.Path.Combine(System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal), "UsdDataProto.db");
            var db = new SQLiteConnection(Path);
            db.CreateTable<usdProto>();


            search.Click += (object sender, EventArgs e) =>
            {
                str1 = ingred.Text;

                var query = db.Query<usdProto>("SELECT * FROM usdProto WHERE Shrt_Desc = ?", str1);

                foreach (var item in query)
                {
                    new AlertDialog.Builder(this)
                        .SetMessage(item.Energ_Kcal)
                        .Show();
                }
            };

        }

        //----------------------------------------------------------------------------

        public class usdProto
        {
            [PrimaryKey]
            public int NDB_No { get; set; }
            public string Shrt_Desc { get; set; }
            public int Energ_Kcal { get; set; }
            public int Protein_g { get; set; }
            public int Lipid_Tot_g { get; set; }
            public int Ash_g { get; set; }
            public int Carbohydrt_g { get; set; }
            public int Fiber_TD_g { get; set; }
            public int Sugar_Tot_g { get; set; }
            public int Calcium_mg { get; set; }
            public int Iron_mg { get; set; }
            public int Magnesium_mg { get; set; }
            public int Phosphorus_mg { get; set; }
            public int Potassium_mg { get; set; }
            public int Sodium_mg { get; set; }
            public int Zinc_mg { get; set; }
            public int Copper_mg { get; set; }
            public int Manganese_mg { get; set; }
            public int Selenium_ug { get; set; }
            public int Vit_C_mg { get; set; }
            public int Thiamin_mg { get; set; }
            public int Riboflavin_mg { get; set; }
            public int Niacin_mg { get; set; }
            public int Panto_Acid_mg { get; set; }
            public int Vit_B6_mg { get; set; }
            public int Folate_Tot_ug { get; set; }
            public int Folic_Acid_ug { get; set; }
            public int Food_Folate_ug { get; set; }
            public int Folate_DFE_ug { get; set; }
            public int Choline_Tot_mg { get; set; }
            public int Vit_B12_ug { get; set; }
            public int Vit_A_IU { get; set; }
            public int Vit_A_RAE { get; set; }
            public int Retinol_ug { get; set; }
            public int Alpha_Carot_ug { get; set; }
            public int Beta_Carot_ug { get; set; }
            public int Beta_Crypt_ug { get; set; }
            public int Lycopene_ug { get; set; }
            public int Lut_Zea_ug { get; set; }
            public int Vit_E_mg { get; set; }
            public int Vit_D_ug { get; set; }
            public int Vit_D_IU { get; set; }
            public int Vit_K_ug { get; set; }
            public int FA_Sat_g { get; set; }
            public int FA_Mono_g { get; set; }
            public int FA_Poly_g { get; set; }
            public int Cholestrl_mg { get; set; }
            public int Gm_unit { get; set; }
            public int num { get; set; }
            public int unit { get; set; }
        }
    }
}

There is definitely data in the Assets file: enter image description here

Answer 1

There are a huge number of things wrong with your code. These are the highlights:

1. the file in your assets folder is not a SQLite DB

2. the table name in the db (once your fix #1) is 'USDADataProto', not 'usdProto'. You are querying table that doesn't exist.

3. Your mapping class should use the correct table name, 'USDADataProto'

4. Your data is in all uppercase, so you need to account for that when querying

like this:

var query = db.Query<USDADataProto>("SELECT * FROM USDADataProto where Shrt_Desc = ?",str1.ToUpper());

foreach (var item in query)
{
  new AlertDialog.Builder(this)
    .SetMessage(item.Shrt_Desc)
    .Show();
}